Security systems have been implemented to monitor residences, offices, stores, or other types of environments. Such security systems typically have two states, corresponding to armed and unarmed modes of operation. The security system for a house, for example, may be unarmed when one or more legitimate occupants are in the house, and armed when no occupants are in the house. It is usually expected that the last occupant to leave the premises will arm the security system upon leaving the house. Conventional security systems typically are armed by entering an arming code or command via a central device, which causes the other components of the security system to enter the armed state.